The present invention relates to a shoe that is easily constructed and provides greater comfort to the wearer without affecting the fit or style of the shoe. The invention has particular utility in connection with high-heeled shoes and will be described in connection with such utility, although the invention also has utility in connection with low heel footwear products as well.
Conventional high-heeled shoes have a reputation for being extremely uncomfortable. There is survey information indicating that as many as 20% of the users of such shoes experience foot pain related to the shoes immediately, and the majority of users experience such pain after as little as four hours of use.
In order to understand the prior art and the present invention, it is necessary to understand the anatomy of the foot and the basics of shoe construction. To that end, FIG. 1 is a diagrammatic view of the bones of the foot and the portions of a shoe that underlie the sole of the foot. By reference to FIG. 1, the following briefly describes the anatomy of the foot and the basics of shoe construction.
FIG. 1 is a diagrammatic medial side view of the bones of the human foot 10. For purposes of this application, references to rearward mean in the direction of the rear of the foot or heel 20; references to forward or toeward mean in the direction of the front of the foot 30 where the toes or phalanges 31 are located; references to medial mean the side of the foot where the arch 40 is located; references to lateral mean the outside of the foot; and references to upper or top and lower, bottom or under assume the foot or shoe is oriented in an upright position.
The heel 20 (also known as the tarsus) includes the talus 21 and the calcaneus 22 bones. The rear lower surface of the calcaneus 22 has a slight protuberance 23 known as the calcaneal tuberosity.
Referring to FIG. 1A, the calcaneus is an irregularly shaped quadrangular bone also called the heel bone or os calcis. As can be seen particularly in FIG. 1A, the medial side of the calcaneal tuberosity, i.e. the lower part of the posterior surface of the calcaneus is not precisely on the same ground or plane as the lateral tuberosity. This slight difference in calcaneal anatomy leads to ankle instability particularly for wearers of high heel shoes.
The bones of the foot also include the navicular 41, the cuneiform 42, the metatarsals 45 and the phalanges, or toes, with the big toe 31 visible in FIG. 1. The metatarsal heads 46 are located at the forward end of the metatarsal shafts 47. The metatarsals are numbered 1 to 5, with 1 designating the big toe.
Also depicted in FIG. 1 is a partially exploded view of the portions of a conventional high-heeled shoe 50 that underlie the sole of the foot. Shoe 50 has a heel 51 which is generally attached to the lower surface of sole 52 of shoe 50, with the sole 52 in turn supporting the insole board 53 on which the sock liner 54 is placed. In a conventional shoe, the insole board is typically of relatively rigid construction from the region underlying the wearer's heel to the heads of the metatarsals. Sock liners are commonly very flexible and generally arc very thin, typically no more than half a millimeter thick. The sock liner is the surface upon which the sole of the foot normally rests.
According to conventional shoe construction methods, the last is the form around which the shoe is constructed. During manufacture, the lower surface of the last sits on the upper surface of insole board, and the shoe upper is then shaped around the last and attached to the insole board. Optimally, the lower surface of the last and the upper surface of the insole board fit together smoothly in order to properly manufacture shoes. If there is any convexity on the lower surface of the last or the upper surface of the insole board respectively, a corresponding concavity must be present in the insole board or last respectively. To be assured of a quality shoe construction, any such convexity and corresponding concavity must be carefully aligned during shoe manufacture, thereby introducing added complexity and/or quality control issues to shoe manufacture.
As will be appreciated, a conventional high-heeled shoe such as shown in FIG. 1 places the rearward part of the wearer's foot essentially on an inclined plane. As a result, the foot is urged forward by gravity into the toe box in standing or walking. This results in pressure on the ball or forefoot regions and toe jamming which often gives rise to a burning sensation in these areas of the foot, as well as fatigue and discomfort in the foot and other areas of the body.
Numerous suggestions have been made for improving the comfort of high-heeled shoes, including suggestions in my prior patents and publications. For example, in a February 1990 article in Current Podiatric Medicine, pp. 29-32, I described a high-heeled shoe design in which the portion of the shoe under the heel does not form a continuous ramp down the arch to the ball of the foot, but rather the portion underlying the heel is relatively parallel to the ground. The design used a rigid plastic molded midsole which was cupped to receive the heel and angled to bring the heel into a plane more parallel with the floor. In addition, a metatarsal pad was incorporated into the molded midsole.
In U.S. Pat. No. 5,373,650, I described a rigid or semirigid orthotic under the heel and extending forward, with arch support, to a point behind the metatarsal heads of the foot. The heel in this device is supported parallel to the ground or tilted slightly backwards.
In U.S. Pat. No. 5,782,015, I described a high-heeled shoe design in which the heel is positioned more parallel or slightly downwardly inclined angle relative to the shank plane and which has an arch support that supports the head of the navicular in approximately the same plane as the wearer's heel bones. My PCT Publication WO98/14083, published Apr. 9, 1998, describes a rigid molded device comprising a heel cup and an anatomically shaped arch appliance.
Numerous examples of designs by others intended to improve comfort of high-heeled shoes exist in the prior art. U.S. Pat. Nos. 1,864,999, 1,907,997, 4,317,293, 4,631,841, 4,686,993, 4,932,141 and 6,412,198 each describes shoe inserts or orthotics intended to improve comfort of a high-heeled shoe. Several involve arch supports. Some are rigid; others suggest cushioning as a means to improve comfort. The prior art inserts and orthotics typically are relatively bulky and can affect a shoe's fit if added by the wearer after manufacture. Other prior art proposals to improve wearer comfort require that each last used to manufacture the shoe be modified to change the shape of the shoe itself.
These prior art constructions improve comfort by supporting or cushioning parts of the foot and/or altering the foot angles to reduce sliding forward and/or to alter the percentage of the wearer's weight borne by different parts of the foot. Their teachings suggest, among other things, placing the heel on a more level plane to shift the weight backward onto the heel, supporting the arch, angling the toes upward and/or cushioning the surfaces on which the largest percentage of weight is borne.
The foregoing discussion of the prior art derives primarily from my earlier U.S. Pat. No. 7,322,132 in which I provide a thin flexible shoe insert which readily can be adapted to any style shoe and which can be incorporated into a shoe without requiring modifications to a shoe last or adding manufacturing complexity. The insert has two slightly raised areas under the heel and the metatarsals. Although the insert has two only slightly raised areas, it significantly increases wearer comfort even in very high heels. The insert does not require that the heel be repositioned to a plane parallel with the floor as is the case in some of the prior art. Other than in the two slightly raised areas, the insert can be extremely thin, thereby minimizing any effect on fit of the shoe and eliminating any adverse effect on the style or appearance of the shoe. Alternatively, the thin flexible insert can be placed in the shoe by the wearer. See also my U.S. Pat. Nos. 7,595,346, 7,814,688 and 7,962,986.